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tRNAs Marked with CCACCA Are Targeted for Degradation

Science  11 Nov 2011:
Vol. 334, Issue 6057, pp. 817-821
DOI: 10.1126/science.1213671

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Abstract

The CCA-adding enzyme [ATP(CTP):tRNA nucleotidyltransferase] adds CCA to the 3′ ends of transfer RNAs (tRNAs), a critical step in tRNA biogenesis that generates the amino acid attachment site. We found that the CCA-adding enzyme plays a key role in tRNA quality control by selectively marking structurally unstable tRNAs and tRNA-like small RNAs for degradation. Instead of adding CCA to the 3′ ends of these transcripts, CCA-adding enzymes from all three kingdoms of life add CCACCA. In addition, hypomodified mature tRNAs are subjected to CCACCA addition as part of a rapid tRNA decay pathway in vivo. We conjecture that CCACCA addition is a universal mechanism for controlling tRNA levels and preventing errors in translation.

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